This disclosure relates to image forming apparatuses and more particularly to an image forming apparatus that forms images by means of a recording head that ejects droplets of a recording liquid.
Conventionally, there is a multifunctional image forming apparatus that integrates the function of printer, facsimile and copying machine by using the technology of electron photography for the image forming part thereof.
Further, there is a multifunctional image forming apparatus that uses the technology of ink-jet recording for the image forming part. With the recording apparatus of this type, a recording head that ejects droplets of a recording liquid called also as “ink”, is used for forming images on a medium, which is called also as “recording sheet”, “recording medium”, “recording object”, or the like, wherein such recording of images is called “recording”, “printing”, “reprography”, “character printing”, or the like.
[Patent Reference 1]
    Japanese Laid-Open Patent Application 2002-192711.
Patent Reference 1 discloses a conventional image forming apparatus that disposes an ink cartridge (ink tank) underneath a sheet discharging tray. Thereby, an ink is supplied to a sub-tank mounted upon a carriage together with a recording head from such an ink cartridge.
[Patent Reference 2]
    Japanese Laid-Open Patent Application 2004-9404
Further, Patent Reference 2 discloses a construction of image forming apparatus in which the medium formed with an image with a recording head is directly discharged to a discharging tray disposed inside the image forming apparatus.
[Patent Reference 3]
    Japanese Laid-Open Patent Application 2001-318494
Further, Patent Reference 3 discloses a construction that enables both face-down sheet discharging and face-up sheet discharging.
With an image forming part that uses an ink-jet process, it is inevitable to provide a mechanism for maintaining and recovering the performance of the recording head that ejects droplets of the recording liquid, wherein it should be noted that the mechanism of maintenance generally includes a humidity maintenance cap that tightly covers the nozzle surface for preventing increase of viscosity of the recording liquid caused by evaporation of the recording liquid, a suction cap, serving sometimes also for the humidity maintenance cap, for sucking and discharging the viscous recording liquid from the nozzle, a wiper blade, called also as “cleaning blade”, “wiper”, “blade member”, or “blade”, for wiping away the recording liquid adhered to the nozzle surface, a dummy ejection part for conducting dummy ejection of the liquid droplets without forming images, and the like.
In the case of the recording apparatus that employs serial scanning process that carries out formation of images on a sheet by causing the recording head to scan over the sheet in a main scanning direction in the state the recording head is mounted upon a carriage, it is practiced to dispose the maintenance and recovery mechanism at an end of the main scanning direction. Further, it is practiced to dispose the dummy ejection part on an end part of the main scanning direction for recovering the nozzle used for recording. Alternately, the maintenance and recovery mechanism is provided at both ends of the main scanning direction as set forth in Patent Reference 4.
[Patent Reference 4]
    Japanese Laid-Open Patent Application 2004-284084
In conventional approaches of constructing the image forming part to carry out image formation by the serial scanning process of liquid ejection head, however, there arises a problem in that the overall size of the apparatus is increased in view of the fact that it is necessary to provide the maintenance and recovery mechanism or dummy ejection part at one end or both ends of the carriage main scanning direction.
Further, while the printing speed itself can be increased with recent image forming apparatuses, there is a need of securing time for drying the recording liquid on the recording medium with such an image forming apparatus as long as the image formation is conducted by using a recording liquid. With this regard, the image forming apparatus that discharges the recording sheet while carrying out image recording simultaneously as taught by Patent Reference 1 or 2 cannot provide sufficient time for drying the recording liquid and tends to cause degradation of recorded images due to rubbing when the printing speed is increased. Thus there has been imposed limitation in the improvement in the printing speed.